The present invention relates to the core shrouds that confine the flow of coolant in nuclear reactors to their core regions.
A nuclear reactor delivers energy by heating coolant that flows through the fuel-bearing core of the reactor. The purpose of the core shroud is to ensure that a maximum percentage of the coolant that is pumped actually comes into contact with the hot core. In a pressurized-water reactor, the shroud is subjected to substantial pressure differentials, so it must be built in such a manner as to enable it to withstand high loads. In addition to pressure loading, further loading must be anticipated from thermal gradients, and, in the event of a postulated earthquake, the shroud must be strong enough to bear the load of laterally supporting the fuel within the core. As a result of these requirements, it is normal to substantially reinforce the coolant boundary panels. The massive shroud structure that results normally requires extensive machining to permit it to closely fit the core boundary for the purposes of coolant confinement and seismic core support, and this machining adds a large number of man-hours to the manufacturing process. In addition, the machining changes the stiffness characteristics of the core shroud, which makes it impractical to "tune" the shroud to achieve the optimum combination of stiffness and shock-absorbing ability.